Currently, dental technicians mostly use two kinds of rotary tool, each of which are made in many different shapes and sizes to cope with the complex shapes of teeth. The number of tools deemed necessary make it complicated and expensive to practise in this field. But also, the tools do not last. One kind has heads which are miniature grindstones, abrasive stone or grit bonded with resin being moulded onto the end of a stainless steel shank. But they tend soon to wear smooth or clog up and they are prone to overheating. It appears that, in the field, no-one has used resin bonded diamond grit which is theoretically the best and most long lasting abrasive. When it has been used, it has generally been adhered by nickel plating to the surface of a stainless steel shank. The problem again is that once the grit is dislodged or worn the tool is useless, and it tends to clog and generate heat. Sintered diamond heads (the diamonds being metal bonded in a mould) have also been tried, but they also clog and overheat.